lincoln



May 17,1921 1,629,280

- E. W LINCOLN TELEPHONE SYSTEM Filed Sept 16. 1922 2 Sheets-Sheet 1 Jul/F712 17f May 17, 1927.

. 1,629,280 E. w. LINCOLN TELEPHONE SYSTEM Filed Sept. 16. 1922 2 $heets-Sheet 2 Patented May 17, 1927.

inn-a8 UNITED s'rares rarer FFICE.

ELMER w. LINCOLN, or CHICAGO, trimmers, assienon re nuances swrrcnnonan AND SUPPLY COMPANY, or CHICAGO, rumors, A CORPORATION or ILLINOIS.

TELEPHONE SYSTEM.

Application filed September 16, 1922. Serial No. 588,549.

My invention relates to telephone system in which manual. linl; or cord circuits are' provided'tor interconnecting telephone lines, and has to do more particularly with systems in which instantaneous automatic ringing, listening, secret service, peg count and instantaneous disconnect and recallare provided.

In cord circuits provided with the abovementioned features, prior to my invention,

and where only one suhscribe1"s line is antomatically disconnected from the cord circuit, eight or more relays are required, and where both subscribers lines are diseonuected trom the cord circuit, nine or more relays are required in the cord circuit to ellect a positiveoperation ot' the system possessing said tcatures, and it is the object ot my relays where single link disconnection is provided to sir-z relays, and to redi'ice the number of relays where double link disconnection is provided to eight relays.

Another teature oft myinvention is the provision of means whereby the calling and called subscribers lines are both automatically disconnected from the cord circuit interconnecting said lines when both subscribers have replaced theirreceivers upon their respective switchhooks, but neither of said subscribers lines will. be disconnected so long as the other snbscribers receiver re mains off its switchhoolr.

Still another feature of my invention is the provision of means in the cord circuit whereby the cord circuit may be used for signaling a called subscriber whose substation is on the same line with the calling sub- SCllllGFS substation, and also tor indicating to the operator when the subscribers have replaced their receivers after conversation.

The above features, as well as others, will be more fully hereinafter described in the tollowing specification.

For a more complete and better nuclei standing of my invention. reference maybe had to the accompanying drawings, Figs. 1 and 2, in which I illustrate my invention operating in connection with a telephone system. The system in Fig. 1 is prolvided with link disconnect means at both ends tor disconnecting both the calling and called sul'iscribers lines from the link circuit. while in Fig. 2 means are provided for only disconnecting the calling subscribers line.

invention to reduce the number ot terminating, respectively, at the exchange in. line c rcuits L and. L. The line circuits L and L at the exchange comprise, respec tively, the usual line relays LR and cut-oil relays CO and CO, multiple jacks MJ and MJ', and the, multiple line lamp sig= nals S and S. The j acksot the lines are distributedamong diilerent operators and there is aline signal for each jack at the operators position so that when a call is initiated over the line the line signals at the operatoi"s positions are lighted, and one of a plurality oi operators may seize the calltothe exclusion ot the other operators.

The cord circuit C for interconnecting the substations A and B as calling and called lines is provided with an answeringplug AP and a callingplugCP, the said answering and calling plugs AP and GP being connected by the heavily marked conductors having the condensers K and K interposed. I

The answering end of the cord has a COI1l bined sleeve and link disconnectrelay SLR, which is energized when the plug AP is inserted into a acl: MJ and tie-energized when the calling and called subscribers have both replaced their receivers upon their respective switchhooks. Said relay de-encro izing disassociates the cord C from tllQllllG circuit L, thereby permitting the calling subscriber to again resumecontrol of the line circuit L to enablehim to initiate another call. regard j less of whether or not the plug AP has been removed :tromthe jack MJ. An answering supervisory relay AS is provided which is energized ovcrfthe calling subscribers line and which relay, when energized. closes an energizing circuit for the operators relay OR and the answering meter magnet AM.

Relay OR operates to connect the operators telephone set to the cord circuit Cyand magnet AM operates to register the number of calls answered by the operator, A guarding relay GR and a high. resistance relay HR are also provided for purposes to be hereinafter pointed out. i

The calling end of the cord circuit C is provided with a combined sleeve and link disconnect relay SLR which. energizes when the calling plug OP is inserted into the multiple jack MJ' and the relay GR is in its tie-energized position. An interrupter ringing relay IR is provided which is energized jwhen theioperator depresses the ringing key RK to Connect one of the ringing generators G, G, G and G to the called subscribers line. A ringing control relay RC'is provided which energizes when the ringing key BK is fully depressed eto connect an interrupter device I in circuit with the upper winding of the interrupter relay whereby relay IR is caused to he intermittently operatedto connect ringing current to the called subscribe us line. "A ;super-' visory lamp SL 1 is,provided jVlllCl'l lightsas soon as the gallingv plug CP is inserted into the multiple jack MJ and remains lighted until the operatordemz sse ith i l ekey RK; the burningglamp SLthus servingasa signal to notify the operator that ringing current has notbeeu connected tothecallod line. Thelamp filiwill also light whenzboth subscribers have replaced their receivers upon the r respective swltchhooks to notify the operatcr that disconncc im is desired.

Referring nowttosthe guarding relay GR,

this ir elay enei'gizes iyvlren both the calling and called subscril ers have replaced their rccei vers ui'ionitheir respective switchhooks. Relay HR will also energize to provide a holding circuit relay Relay GR energizing opens ,theholding circuit of the relay SLR; which relay @LR' will don energize .to dissociate the answeringend of te l ng and Caller the cord circuitlC from the multi ple jack IMJ, thereby freeing the calling subscribers line and line circuit Belay energiz- .ing also opens .theih'olding circuit "of relay SLR. which will cause relay SLRto d ejenergizeto dissociatethecord circuit C from the multiple jack'MJ, thereby freeing .the called subscribefls .line and line circuit L.

Should the calling subscriber replace his receiver upon its sw-itchhook before .the called subscrlbejr responds, relay QGR will energize to open the-,hqldingcircuit of relay SLR andtheliolcling circuit ot relay SLR;

thus automatically disconnecting ringing current from the cord circuit and also freeing the calling and called subscribers lines ftrom the i cord circuit C.

Referring now in general to the syStem m Fig. 2, which (is a modification of the system illustrated in '1, it comprises a substati on .D- andE, termis If mi 1 a p Circui'ts arranged natin'g in line on y s d 1 im identically the same as line circuits L and L in Fig. ,1 The .QircuitQG is prov ded w th an 311$, pfi ug Al? and a calling plug CP, wine are interconnected by the h avi lea e ondui a having condensers fland K interposed. The

a i. iw flisp d th H m in -i are n i k disanswering end of t e cord C fcon n' ct rekiv' ,yqhich energizes when tl is inserte nt-Q mul p ,GLG, G or G to the called line to signal -in circuit with the interrupter relay IR,

'to ,the n'inltiple jacks and the calling subcdetaillthe operation oi the @the substation desires to coxrrerse with the closing a circuit for the lll'lt contact 1 of cut-otl' re closed contact of relay .of operators positions.

jack MJ Relay SL11 energizing closes a circuit for relay AR, which relay AR operates to close a circuit for the answering meter relay AM, which in turn energizes to close a circuit ior the relay MR, which relay llll-l operatcs to register the number of calls answered by the operator. A relay Olt is provided for automatically con11ecting the,operatoristelephone set to the cord circuit when the plug AP has been inserted 7 iutom multiple jack hill and relay SLR i has operated.

'l-he calling end of the cord circuitCl is provided with a calling sleeve relay CSR which energizes when the calling plug Cl? is inserted into a multiple jacz MJ A ringing interrupter relay IR is provided and operates when the ringing key BK is depressed to connect one of the generators the called subscriber thereon. A slow-act'- ing ringing control. relay BC is provided which energizes when the ringingkey 11K is operated to connect an interrupter device thereby causing ringing current to be intermittently applied to the called subscribcrs line. Relay RC remains energized so long as the (plugs AP and CP'are connected scribcrs receiver is ren'ioved from its switchhook and thecalled subscribors receiver re mains on vits swltchhook. A supervisory llamp SL is providcdwhich lights as soon ,as the plug CP is inserted into a multiple loo jack MJ and remains burning until the ringing key BK is operated to connectiring lng current to the called .suhscriloers line,

said lamp serving as a signal to notify the operator whether or not ringing current :has been connected to the called line. Lamp Sll will also burn when conversation has-terminated and both subscrihors'hang up iTllQll receivers to indicate that connection is no longer desired.

J10 Referring now more in detail to thaopcration otn'iy'invention, I will 5 dcs the in a illustrated in 1 Assuutiing that the subscriber at 1) 17;, lie

subscriber at the substation will move his receiver from its ,switc from battery, windi lity Assuming that cord circuit C that answers will be lighted over this circuit the operator at the call, the insertion of the answering plug ill? into the jack Mil ot the callingline establishcs a series energizing circuit for the cutoll relay (it) oi the line circuit L and the combined sleeve and lint disconucct re lay ltllilsl, the circuit l'ieinp; traced 'lroin battery through the wini'lii'ig" ti and T of relay normal contact. o oi relay Git, con-- dnclor ll, sleeve contacts of the plu ll and through the lower winding; of relay AS, al-

ter ate contact '11 ot relay SLR, ring: con tacts 0t plug AP and jack rill, through the substation A. tip contacts o'l jack MJ and plug All, alternate contact 12 of relay SLR, to ground through the upper winding 01 relay AS. The high resistance winding T oil" the relay SLR is shunted, this arrangr mout iroviding for secret service, as a relay SLR of a second cord circuit will not operate in series with the relay (0 as the shunt ot the low resistance,Winding is oil? the relay SLR oi the first cord circuit renders the relay SLR ot the second cord circuit inoperative. The operation oi relay CO causes relay Lilto restore, thereby causing the etl'acement of the lamp signals S. Relay AS en ergizinp; closes a circuit for the operators relay OR, which'energizes to connect the op erators telephone set in circuit with the call- .inp; subscriber s line, said circuit being traced from battery, tl'irough the Winding of relay OR, conductor 13, alternate contact 1% of relay AR, conductor 15, to ground through normal contact 16 of relay SLR. Relay AR also closes a circuit for the answering meter magnet AM, which energizes to operatethe registering device to register the nun'iber of calls answered by the operator. The circuit for magnet AM may be traced from battery, ii-hiding of magnet AM, alternate contact 14 of relay AS, conductor 1!, normal contact 16 of relay SLR, to ground. i

The operators set 0 now being; connected in circuit with the subscriber at the calling; substation A, she will inquire the wants of said subscriber, and assui'ninp; that he desires to converse with the subscriber at substation B, the operator will make the usual test to determine the busy or idle condition of the called subscribers line in the well known manner; and. assuming that'thc line is found to be idle, the operator will insert the calling plug GP into the jack MJ', thereby bringing about the operation of relay SLR and. the cut-oil relay CO in series, the circuit for said relays being traced from battery, through the winding of said relay SLR, conductor 18, normal. contact 1.9 oil, relay till, conductor 20, sleeve contacts of relay Cl. and jack Mil, to ground throl igh the winding of the cut-ott relay CO. Relay Ct) operating removes the line relay LR from the control of the called subscriber B so that when the called subscriber answers, the lamps S will not light. Relay SLR energizing opens the energizing circuit of relays OR and AM at normal contact 16, thereby disconnecting the operators set from the cord circuit C to provide secret service and to prevent the further operation of the registering device. The operator will now depress the proper ringing key plunger of the party-line ringing key BK to'its fully depressed position toclose the end spring contact 21 and'to connect the proper ringing generator .G, G, G or to signal the called-for subscriber at substation B. The closing of alternate contact/21. of thecnd springs brings about the energization of the interrupter relay IR, during the interval of that the key is held down, over a circuit traced trom battery, through the upper Winding of relay IR, alternate contact 21 of the end spring, conductors 25 and 43, to ground through alternate contact 16 of relay SLR. The closing of alternate contact 24 ofrelay IR connects ringing current from the generator (i Which We will assume is the generator selected to ring the call bell of the subscriber at substation B, giving an instantaneous first ring to the called subscribers bell, The closing of alternate contact 22 of the end'spring of the key plunger closes a circuit for ringing control relay BC, traced from battery, winding of relay RC, alternate contact 22 of the end spring, conductors 25 and 43, though alternate contact 16 of relay SLR to ground. Relay energizing over this circuit establishes a looking circuit for itself, traced. from battery through the winding of said relay'RC, its alternate contact 27, conductor 28, normal contact 29 of relay GR, conductorBO, normal contact 23 of relay CR, conductor 43, alternate contact 16 of relay SLR, to ground. The opening of normal contact 31 of relay RC eflaces the supervisory signal SL. The closing of alternate contact 32 of relay RC connects the interrupter I to the lower winding of interrupter relay IR, the circuit being traced from battery, through the lower winding of relay IR, alternate contact 32 of relay BC, to ground through the constantly rotating interrupter device I. The relay Ill is thus intermittently energized and ale-energized to con nect ringing;- current from generator G to the called line over a circuit traced from ill) ltll) the ungroundcd pole of the generator G to conductor 90,- alternate contact 24L of the relay IR, conductor 91, alternate contact 92, of relay SLR, tip contacts of the connected plug G1 and jack MJ through the call bell and condenser at called substation B, back through the ring contacts of the jack MJ and plug GP, alternate contact 93 of relay SLR, conductor 9st to ground at alternate contact 95 of relay IR.

The closing of alternate contact; 34- of relay IR transmits a ringing tone to the calling' subscriber at substation .A, the ringing tone being traced from the ground through the generator G, over conductor 36, alternate contact 34; otrelay IR, alternate contact 12 of'relay SLR, tip contacts of plug AP and jack MJ, through the receiver at substation A, ring contacts jack MJ and plug AP, alternate contact 11 of relay SLR, lower winding of relay 'AS to battery, giving the calling subscriber at substation A an audible signal notifying him that the called subscriber at suliistation B is being signaled. The called subscriber at the substation B is thus automatically signaled until. he answers in response to'his call signal or until the calling subscriber replaces his receivcrbefore the said called subscriber answers.

Shouldthe calling subscriber replace his receiver before the called subscriber answers, the answering relay AS will restore, due to the interrupted switchbook contacts at the calling substation A. The closing of normal contact 38 of relay A'S closes an energizing circuitfor relay GR, traced from battery through the winding of said relay GR, normal contact 39 of relay CR, conductor {10, normal contact 38 of relay A'S, alternate contact 41 of relay SLR, conductors 42 and 43 to ground at alternate contact '16 of relay SLR. Relay GR energizing opens its normally closed make-before-break contact 19, thereby opening the circuit of relay SLR, Wherebysaid relay restores, and also closes a circuit for the high resistance relay HR, which will operate to close a holding circuit for relay GR, traced from battery, winding of relay GRto ground at alternate contact 45 of relay HR, the circuit {for relay HR beingtraced from battery, winding of saidrela-y' HR, alternate contact 19 of relay GR, conductor 20, sleeve contacts of plug CI and jack MJ to ground through the winding of cut-oft relay CO. Relay CO will not operate over this circuit due to the high resistance of relay 'HR, nor will the line test busy, since the potential upon the jack MJ Will not be sufficient to energize the test relay TR in the operators circuit. Relay GR upon energizing opens normal contact 8, thereby opening the holding circuit of relay SLR. Relays SLR and SLR tip contacts of jack hto scribcrs lines.

restoring disassociate the cord circuit C from the calling and called subscribers lines, respectively, and relay GR energizing opens the circuit of ringing control relay R0 at its normal. cont-act 29, whereupon relay RC restores to bring about the disconnection oi ringing current from the cord circuit C. "Ti lie calling and called subscribers lines are now free and either subscriber may initiate a call or be called, as the case may be.

Assuinii'ig, however. that the calling subscriber does not replace his receiver and that the called subscriber at substation l3 removes his receiver during a silent or non-ringing period, that is, when relay IR is in its dcencrgized position, a circuit will be closed for the relay CR over a circuit traced from battery, through the lower winding of relay CR, normal contact 95' of relay IR, alternate contact 03 of relay SLR, ring contacts of plug GP and jack MJ, through the now closed switchhook contacts of substation 13,

and plug Cl, alternate contact of relay SLR, normal co-ntact 2-l of relay IR, upper winding oit relay CR to ground. 'Rclay CR will not energize when in series circuit with the call bell and condenser at the called substation B, due to the combined high resistances of said call bell and condenser. Relay CR having onergized over the above traced circuit opens the locking circuit or the ringing control relay RC at its normally closed contact 23, which causes relay RC to restore to close its normal contacts 4-7 and 50 in the talking conductors ot the cord circuit C, and to open its alternate contact 32, thereby opening the circuit; through the upper winding of relay IR to prevent the further operation of relay IR and the application of ringing current to the called line.

The called and calling subscribers at the substations A and B are now in conversational circuit, the talking circuit being traced over the heavily marked conductors. After the subscribers have finished conversation, they replace their receivers upon their respective switchhooks, causing the relays AS and CR to restore, due to the opening of the switchhook contacts at the respective substations. Said relays restoring close their normal contacts 38 and 39, thereby closing a circuit for relay GR, the circuit being the same as has already been traced. Relay GR energizing, relay HR will energize,.and relays SLR and SLR will (lo-energize to disassociate the cord circuit C from the sub- Lamp signal SL will light over a. circuit traced from battery, through the lamp SL, normal contact 31 of relay RC, conductor 30 to ground at alternate contact 29 of relay GR, to notify the operator that conversation has terminated. The operator will now withdraw the plugs AP and GP from the jacks MJ and MJ, whereupon re laysGR and HR will restore to normal and the cord circuit will. be in readiness for another connection.

Reverting no w to when the operator tested the called line, and should the called subscribei."s line be busy either as a calling or a called line, there will be a battery potential upon the sleeve contact ot the multiple jack Mil so that when the operator touches the tip oi the calling plug Cl? to said sleeve contact, a circuit will be closed for the busy test relay TR, traced from battery at the sleeve of said. multiple jack Md, tip contact oi? plug Cl normal contact of relay SLR, conductor H, to ground through the windingot the test relay TR. Relay TR energizing over this circuit closes its alter nate contact 72. which closes a circuit throiiigh. the tertiary winding (a? the opera tors set 0 to give her the usual wellknown click in the ear to notify her that the line is busy, said circuit being traced troni battery through the wil'iding of coil 73, alter nate contact 72 of relay TR to ground. Helay TR will only operate to give a busy signal when the called line is actually busy and in ronvcrr aational circuit, but will not oper ate when the high resistance relay HR of a cord circuit connected to the called line has operated after the termination of conversation, tor in this instance the battery potential upon the sleeve contact of the jack MJ trom the relay HR is not suiiiciently strong to o 'icrati-z the test relay TR in the operators circuit.

Assuming now that the calling subscriber desired to tall: with a subscriber SS who is on the same line with said calling subscriber but only indicated onthe drawing by lines 3 and it which are tied to line conductors 3 and at respectively and lead to the sub station 01" the subscriber SS, the saidsubstation being indentical in construction and operation as substation A, the operator Wlll answer the call in the same manner as before described, and. upon learning that the subscriber wanted is on the same line with the calling subscriber, she will notify the calling subscriber ot this fact and wilhtell him to hang up his receiver while she rings the called-torsubscriber. The operator will withdraw the answering plug AP from the jack MJ and will insert the calling plug Cl into the jack Md, thereby closing a cir cuit for relay SLR, traced from battery, through the winding of said relay SLR, conductor 18, make-be'torebreak contact 19 of relay GR, conductor 20, sleeve contacts of plug GP and jack Md to ground. through the cut-otl:' relay CO. Relay SLR energizing closes a circuit for the lamp SL, which will. burn until. the operator depresses the ringing key plunger oft ringing key BK, said circuit being traced from battery throughlampSL, normal contact 31 of relay RC, normal contact 23 ofrelay CR, conductor a3 and to ground at alternate contact 16 of relay SLR. The burning of lamp SL at this time will notify the operator that the ringing key has not been operated, and she will then operate the proper ringing key plunger ot' the ringing key RK to connect the proper frequency generator, which we will assume is the generator G6, to ring the called-tor subscriber. lVhen the key plunger is in its fully depressed position, alternate contact 21 of the endspring is closed to establish a circuit for the interrupter relay IR, traced from battery, through the upper winding of relay IR, alternate contact 21 of the end springs, conductors 25 and 43, to groul'id at alternate contact 16 of relay SLR. Ringing control. relay RC will also energize when the key plunger is fully depressed, over a circuit traced from battery, through the winding of said relay RC, alternate contact 22 of the key plunger, conductors 25 and 43 and to ground at alternate contact 16 of relay SLR. Said relay RC energizing will close a locking circuit for itself traced from battery, through the winding of said relay RC, its alternate contact 27, conductor 28,

normal contact 29 of relay GR, conductor 30, normal contact 23 of relay CR, conductor 43 to ground at alternate contact 16 of relay SLR. Relay RC operating opens the circuit of the lamp signal SL at its normal contact 31, and closes its alternate contact 32 to connect the interrupter device I in circuit with the lower winding of relay IR. Relay IR will intermittently energize and de-energize to intermittently ring the called subscriber. hen the called subscriber answers and the relay IR is in its de-energized position, a circuit is closed for relay CR including the now closed contacts of switchhook at the called subscribers substation. Said relay CR operating opens the circuit of relay RC at normal contact 23 of relay CR, whereupon relays RC and IR restore to prevent further application of ringing current to the called substation. After a reasonable time has elapsed the calling subscriber removes his receiver and the two subscribers are now able to converse with each other.

After conversation has terminated, the subscribers replace their receivers upon their respective switchhooks, thus opening the circuit of relay CR at the switchhooh contacts, and relay CR restoring closes a circuit for the lamp SL, which will now light to indicate that the connection may be taken down, said circuit for the lamp SL being the same as before traced. The operator seeing the burning lamp will withdraw the plug GP from the jack Mil, whereupon relays SLR and CO restore and the lamp SL is eifaced, thus rendering the cord circuit 0 available for another connection.

Operation of system ilbustratcd in Fig.

Assuming that the subscriber D removes his receiver from its switchhook to initiate a call,- a circuit will be closed for the line relay LR traced from battery, winding of relay LE normal contact 101 oi cut-oii' relay CO line limb 102, throughthe substation D, line liinb 103, toground through normal contact 104; of relay CO Relay LE energizes, closing a circuit for the line lz'unlis S which lamps willl'ight before apluiality of operators. Assuming thatit is the operator at cord circuit C that answers the call, the insertion of the plug AP into the jack-MJ of the calling line establishes a series energizing a circuit for the combin'ed sleeve and link disconnectrelay SL11 and cut-oil relay CO said circuit being traced from batter through both windings 105 and 106 of re ay SLR condiu-tor 107, normal contact 108 of relay ()Slt, conductor 109, sleeve contacts of pity-gill? and jack MJ to ground through the winding of cutoff relay CO Relay CO operates over this circuit to open its normal contact 101, thereby opening the circuit of relay LIV, which restores to cause, the ciiacenient oi the lamp signals S Relay SLR energizing closes its alternate contacts 110, 111., 112, 113 and 114, said alt-eri'iate contacts 110 and 114 closing a circuit for the relay 4. l, traced'froin battery, through the .lower Winding of the relay AR, alternate contact ll l of relay SLRE, ring contacts of plug AP and jack MJ through the substation D, the contacts of jack MP and plug iiPf, alternate contact 110 of relay SLR through the upper Winding of relay AR to ground. Relay AR energizing closes its alternate contact 115 to close a holding circuit for relay SLR? and closes its alternate con.- tact 116 to close a circuit for swering' meter relay AM, which will energize to close a circuit for relay MR to cause the same to operate the call regi==tering mechanism, whereby the number of calls answered by the operator atcord circuit C is registered, thecircuit tor relay AM be ing traced from loattery, through the winding of relay AM, alternate contact 116 of relay. AR, conductor 117, normal contact 118 ofrela CSR to ground; and the circuit for relay 1R being from battery through the winding of relay Ml, alternate contact 119 of relay AM to ground.

Theclosure of alternate contact 112 of rc-.

lay SLR upon its energization closes a lower resistance circuit through its winding 105, this circuit being traced from battery, through winding 105 and alternate contact- 112 of said relay SLR alternate contact 115 of relay AR, sleeve contacts of plug the an- AP and jack MJ to ground through thewinding of cut-off relay C0 The high re sistance winding 106 of relay SLR is shunted by the circuit just traced, and by this arrangement secret service is provided, since a relay SLR of a second cord circuit will not operate in series with the relay CO as the shunt oi the low resistance winding 105 of the relay SLR of the first cord circuit renders the relay SLR ot' the second cord circuit inoperative, thus preventing the operators telephone set from being connected to the second cord circuit.

lVhen relay SLR of. cord circuit-C euergized, a circuit was closed for the relay OR, which relay operates to connect the operators telephone set in circuit with the calling subscribers line, said circuit being traced from battery, through the winding 01 relay OR, alternate contact 111 of relay SL11 conductor 117, normal contact 118 of relay CSR to ground. The operato1"s teleihone set 0 is now connected to the talking conductors of the cord circuit C, through alternate contacts, 120 and 121 oil relay OR, conductors 122 and 123, norn'ial contacts 12 and 125 of relay CSR and conductors 12-1; and 127. The operator now inip ircs the wants of the calling subscriber at the substation D, and assuming that the subscriber at substation E is wanted, the operator will make the usual well-known test to determine the idle or busy condition. of the called subscribers line, and assuming that said line tests idle, the operator will: insert the calling plug GP into the jack MJ thereby closing a series circuit tor the calling sleeve relay CSR and cut-oii' relay CO,said circuit being traced from battery. through the winding of the relay USE, sleeve contacts of plug CP and jack Md", winding of cut-oii' relay 60" to ground. Relay CO operating over this circuit removes the relay LE from the control at the called subscriber at substation E to prevent the lighting of the line lainp signals S. and relay CSR energizing opens its normal tontacts 124; and 125 to disconnect the operators telephone set 0 from the cord circuit C. The operator will now depress proper ringing key plunger 01 the party line ringing key RK'to its fully depressed position to close the end spring contact 12,;

LI, int.

and to. connect the proper frequency ring fit relay CSR to ground The closing of alternate contact 131 '1. relay Ill, connects ringlug current- :t'rom the generator G, which we will assume is the generator selected .to ring the call bell oi the subscriber at substation ll, giving an instantaneous first ring to the called subscribers bell. The closing or? alternate contact 13d of relay LR closes an energizing circuit tor the ringing control relay R l, traced from battery, Winding; ojt relay RC, conductor 135, alternate contact 134. oi. relay Ht, conductors 136 and 129, alternate contact 113 of relay SLBP, conductor 1.30 to ground at alternate contact 11.8 of relay CSR. Relay RC energizing over this circuit establishes a locking circuit for itsell. through its alternate contact 13?, con ductor 1411, normal. contact 14-2 of relay GS, conductor 199 and over the remainder of the previously traced circuit. Relay RC having; operated, an interrupter device l is c uuccted in circuit with the upper whirling of the interrupter relay lit, whereby said relay l lt is caused. to energize and de-energize to intermittently apply ringing current to the called subscribefis line, said circuit being traced from battery, through the upper winding); ot relay IR, alternate contact 138 0:1 relay EC, to ground throuoh. the constantly rotating interrupter device l. The called ior subscril'ier is now intern'iittcutly Slg i llftlQCl.

Should the operator .iail to depress the plunger ot the ringing hey BK upon the in sertion oi? plue' Cl? into the jack Mil, re-

lays ill and .tC will not operate and a cir will be established for the lamp signal Li traced from the battery, through the lamp t ll], normal contact 137 of relay PC, conductor 141.. normal, contact 14412 of relay Uri, conductor .129, alternate contact 113 of relay SLR, conductor 130, to ground at alternate contact 118 of relay Lamp 11'? will ligrht over this circuit to notify the io 'ieratoi." that she has not operated her ring inn hey to signal the called sul-iscriber.

Should the calling subscriber at substa-v tion D replace his receiver upon its switchhooh before the called subscriber answers, ringing current will be automatically disconnected from. the called line due to the fact that when subscriber lD replaces his receiver relay All will (lo-energize to cause relay will to (lo-energize, which relay filial-l dernernizing opens the locking" circuit of, relay til at its alternate contact 1.13, causing said relay R0 to d cne to open. the circuitol relay lit at alternate contact 138 of relay HQ. but assuming}: that the subscriber l) (loos not replace his receiver but thatthe called subscriber l l reniioves his receiver to answer the call during a silent or none-ingriugi period, that is, when relay 1P. is in die-energized position, a circuit will be closed for relay CS to cause the same to operate to prevent the further application of ringing current to the called line, said circuit being traced from battery, through the lower winding 01 relay CS, normal contact 132 of relay 1R, ring contacts of plug C1 and jack Mu through the now closed switchhook contacts of substation E, tip contacts of jack MJ and plug; OP, normal contact 131 of relay IR, alternate contact 1 of. relay CSR. to ground through the upper winding of relay CS. Said relay l8 operating over this circuit opens the holding circuit of the ringing control relay RC at its normally closed contact 1 12, whereupon relay RC (lo-energizes to open the circuit of relay IR at contact 138 of said relay RC. Relay CS will not operate when in series circuit with the call hell and con denser at substation E, due to the combined high resistances ofsaid. call bell. and condenser, but will energize when the receiver .switchhook thereat is raised to close a shunting circuit about said call bell and condenser. Should the called subscriber move his receiver during a ringing period, nothing will happen, since at this time relay IE will be energized and the normally closed contacts 131 and 132 in the circuit of relay CS will be open, but just as soon as the relay IR de-energizes, relay CS will energize as before described. The ringing; current for operating the call bell of the called snbscribers substation E may be traced. from ground through the generator G (since we have assumed that generator G is the proper generator), closed contact of the ringing key BK, conductor 1 6, alternate contact 131 of relay IR, tip contacts of plug CPand jack M91 condenser and call bell of substation E, ring contacts ot jack MP and plug GP to ground at alternate eontactlSQ of relay IR. A revertive ringing tone is transmitted to the calling substation D to notify the subscriber thereat that the called-tor subscriber is being sig naled, this circuit for the revertive tone bein o; traced. from ground, through the generator t l", condenser C, alternate contact 133 of relay IR, conductor 147, alternate contact'l lO of relay RC, alternate contact 110, of relay SL11 tip contacts of plug AP and vjack 115 through the receiver of the sub station D, ring contacts of jack MJ and plus; AP, alternate contact 1.14; of relay S1 lower winding of relay AR to bat tery and ground.

The called and calling subscribers are now in conversationalcircuit, the talking circuit being traced over the heavily marked conductors. After the subscribers have finished conversation, they replace their receivers upon their respective switchhoohs, causing the relays AR and C8 to restore, due to the opening of the switchhook contacts at the respective substations. Relay All de-energizingi'opens its alternate contact 1 15, thereby openingithe holding 'en 'cuit' of relay SLR, whiclr relay SLR restores t'odiscs sociate' the cordcireuit C from the callin f" subscribers line so that the subscriber at sul station Dinay initiate new call and light' the. line lamp signals S even {though t plu AP ren'iains in the jackMJ CS restoring" closes its norma l con'tact143,- which nrturn closes a circuit for the lampsignal SI]. traced from battery, througl'i the lan'ipSL, normal oontzictlZ-li of relay HQ). conductor H 1, normal comma-1114 3 of relay- (lS, i'un-malcontact 11 otrehiy SL11 con durtor 3( to groundat alternate contact r r 1 118. lhe operator observing the lighted;

lamp S'L will know thatconversation has lern'iinatcd' and wiliwiiii-draw theplugis U?" and Cl? from the-jacks MQ andlrEJ', re-' spectively, whereupon relay 'CSR restores and thc-lan'ip S12 is restored Sllfifllld" called suliscriber at: substation F m recall, he'i'uay get-rho attention of the opera-tor by? winkiingl his switchh'oolr, Wl iiclrwill open and close the circuit-oi? relay CS" to cause the same to energize and (lo-energizeto' cause th 'efllan'ip signal SL to burn intermittently .to'rotily the operator that her attcnion is waiited-by theca'lled sub- ".-;criber, whereupon' the operator proceeds to answer thecall in thesam'e manner HSl'HF-O inbciore described;

(Jr/Ned subscriber 0w, callz'oi .s'ulis'm ibcrs Zinc.

Assiiiming now that the callingsubscriber has initiated a call and that the operatorat cord-circuit C has answered the same in the manner described above, and that the subscriberwan ted by'the calling subscriber at substation Dds the subscriber SS"which is on the same line with substation D, but only indicated on the drawing. by the conductors 102 and 103 which arertied to the telephone line conductors 102' and 103 respectively, suidconductors 102 and103 extending to the substation of the subscriber SS", the" jack MP; and will then insert the calling plug GP into the ack MJK thus completing a series circuit for the cal-lingsleev'e relay CSR; traced I from battery through the winding of said relay CSR, sleeve contactsof plug (,P and jackMJ to ground'through the winding of cut oi'f relay CO Relay CO will operate overjthis circuit to prevent the lighting of the line lamp signals S and relay CSR will: also-energize. 'lhe'operator" will now depress the-proper ringing key plunger of theri'nging key BK to its'inaio imam position te close alternate contact'128 of the end spring-oi said ringing key, thereby' closing a circuit for the interrupter relay IR", traced from battery, lower winding of relay IR, alternate contact 128 oi the end spring of key RE, normal contacts 112' and 143 of relay CS, normal contact 113 01? relay SL11 conductor 130, to ground at alternate contact 1118 of relay CSR'. The closure ofalternate contact 131 of relay IR connects lialitrry', through tlu r winding of said relay.

RC, conductor 135, alternate contact 134: of relay 1R, coinluctor' lSll, normal contacts and 1' 1 3oi relay CS, normal contact 113 of relay SE1 conductor 13( and to ground at alternate contact 118 of relay CSR. Said relay RC operates over this circuit to connect ihe intei aptor device I in circuit with the upper wind-inc; o'irclay 1R to cause the same to operate intermittently to ring the called subs i ber, as dcscriliied in the lorec ngde'su ption. Relay '1 also closes a locking circuit for itself, traced from batry tl'irouglrits winding and alternate con- 137,, conductor 141, normal. contact 1453 oi rela y CS, and over the previously traced circuit. Should the operator fail to depress thc ringing'key BK, the lamp signal SL will. light over a circuit traced from battery through said lamp SL, normal contact 137 of relay RC, conductor 1 11, normal contact 14:3 or relay Cr", normal contact 1123 of relay SLR, conductorlSO, to ground at alternate contact 118' of relay CSR; this lamp SL burning at this time notifies the operator that the ringing key has not been operated.

The called-for subscriber is now being intermittently signaled, and should the called subscriber answer during a non-ringing period the relay CS will energize to prevent the further application 01? ringing; current, or should said'subscriber answer duringa ringing period,- relay CS will not energize until after relay 15: has (lo-energized. This part oi the operation of the svstem will be clearly understood from the foregoing de scription and arepetition of the same is not deemed necessary.

After a reasonable time has elapsed in which the called subscriber may be signaled. the calling subscriber will again remove his receiver and the two SUlJSCI'il'JGiS will then be able to converse with each other. Alter conversation has terminated, the subscribers will replace their"reccivcrs'upon their TGSPGCtlVQ S'W'itCl'ihOOlKS, thereby opening the circuit for relay CS, whereuponrelay CS restores to close its normal contact 143 in the circuit of the lamp signal SL, which lamp SL will light, and at this time serves as a signal for (flisconnection. Should either the calling or called subscriber desire to recall, he may ob-' tain the attention of the operator at cordcircuit C by winking his switchhook, which will open and close a circuit through the relay .18 to cause said relay CS to energize and de-energize to open and close its normal contact lei-3 in the circuit of the lamp signal till. thus causing the lamp signal Sl/ to flash, which will notify the operator that her attention is desired, and she will. then proceed to answer the cally in the same manner as betore described.

l l hile I have illustrated and described a particular en'ibodin'iel it of my invention, it is to be understood that I do not intend to be limited to the particular structure Which herein described and illustrated, but intend to cover all such changes and modifications as come within the spirit and scope of the appeinled claims.

Having described my invention what I claim as new and desire to secure by Letters Patent is:

1. In a telephone system including only telephone lines, link circuits for interconnecting the same, said link circuit-s provided with automatic listening means, automatic instantaneous ringing means operable at regular intervals after said instantaneous ringing, secret service means, and a pair of link disconnect relays for controlling contacts during the completion of a connection and during conversation comprising means operable by subscribers interconnected by one of said link circuits upon termination of conversation and inoperable when only one end of one of said link circuits is used in. intel-connecting subscribers on the same line.

2. Ina telephone system including subscribers telephone lines, operators link circuits for interconnecting said lines, a combined sleeve and link disconnect relay for closing contacts in the talking conductors of a link circuit when said link circuit is connected to a subscribers line, and automatic nnaus controlled over said subscribers lines to cause said relay to operate to operatively disassociate said link circuit from said subscribers line, said means inoperable to operate said relay to disassociate said link circuit and subscribers line when only one end of said link circuit is used.

In a telephone system including a calling and a called subscribefis telephone line, a cord circuit for interconnecting said telephone lines in conversational circuit, a pair of combined sleeve and link disconnect relays lor closing contacts in the talking conductors of said cord circuit and also for disassociating said cord circuit and said telephone lines when both subscribers hang up their receivers but inoperable if the called subscriber is on the same line with the callwhen both subscribers have replaced their, receivers upon-their switchhooks to disasso-' ciate said subscribers telephone lines and said llnk circuit, automatic ringing means tor signaling the called subscriber, and a supervisory lamp for indicating whether or not ringing current is being applied to the called line, said lamp also indicating the ter mination oi? conversation. V

5. In a telephone system including subscribers telephone lines, link circuits for in tel-connecting said lines in conversational circuit, a double-wound combined sleeve and link disconnect relay individual to said link circuits and adapted to be energized when a link circuit is connected to one of said tele* phone lines to operatively associate said connected link circuit and Said telephone line, means'f'or preventing more than one of said link circuits from being operatively connected to the same line at the same time, automatic ringing means for said link circuit :for applying ringing current to the called subscribers line, automatic means for disconnecting ringing current from the called subscribers line when the calledsubscriber answers or the calling subscriber replaces his receiver upon its switchhook, means for automatically operating said relay when the calling subscriber hangs up his receiver to operatively disassociate said link circuit and said calling subscribers line, and a supervisory lamp effaced when ringing current is applied to a called subscribers line to pro vide a dark key shelf and operated toindicate the termination of conversation.

6. In a telephone system including telephone lines, link circuits for interconnecting said lines in conversational circuit, a pair of combined sleeve and link disconnect relays individual to said link circuits and operable when connection is made with said lines to control contacts in said connected link circuit, energizing circuits for said relays, a third relay for controlling the energizing circuits of said pair of relays, and an energizing circuit for said third relay controlled jointly over the calling and called subscribers lines, said third relay operating to cause the restoration of said pair of relays to operatively disassociate the calling and called subscribers lines from said connected link circuit.

7. In a telephone system including a calling and a called subscribers telephone line, a link circuit for interconnecting the same,

said linkcircuit having automatic listening,

secret service, a counting magnet, and automatic ringing means, a. pair of combined sleeve and link disconnect relays for said link circuit, circuits for said pair of relays, a third relay for controlling contacts in said circuits, said third relay operable only when the'recei'v'ers the calling and called substations are in their normal positions to effect operation of said pair of relays Whereby said calling and called telephone-lines are-freed from said link circuit.

8. In a telephone system including telephone lines, a plurality of link circuits for interconnecting said lines, a combined sleeve and link disconnect relay individual to said link circuits, and operable when its asso ciated link circuit is connected to one of said telephone lines to operatively conn-ct said connected link circuit to said telephone line, a relay controlled over the callingsubscribers line, said second relay controlling the restoration of said combinec sleeve and link disconnect relay whereby said calling subscribers line is operatively freed :t'rein saidlink circuit although a physical connection remains between said line and said link circuit, and a supervisory signal controlled jointly by the calling andcalled subscribers for notifying the operator when conversation has terminated.

9'. In a telephone system including subsc'ribers" telephone lines, link circuits for interconnecting, said lines in conversational circuit, automatic ringing; means for ringing the calledsubscriber, a combined sleeve and link disconnect relay individual to the answeringand calling ends of said link circuits and operable when its associated link circuit is connectedto'said subscribei"s line: a third relay controlled jointly by the calling and-called subscribers, said third relay controlling the operation of said combined sleeve and link disconnect relays whereby the calling and called subscribers lines are operative disassociat-ed from said link circuit', said link disconnect relays inoperable to disconnect the subscribers line from the link circuit when both the calling and called subscribers are on, the same line.

10. In a telephone system including subscribers telephone lines, a plurality of link circuits for interconnecting such telephone lines, automatic link disconnect means individual to said link circuits and operable when a link circuit is connected to different subscribers lines, said means operable l'or controlling; contacts to complete the connection and during conversation, automatic means controlled jointly by the calling and called subscribers for causing: the restoration of the link disconnect means in said link circuit whereby said link circuit and subscribers lines are operatively dissociated from each other, and means for preventing the operation of said link disconnect means to-disissociate said link circuit and subscribers line when both the calling and called subscribers are on the same line.

11. In a telephone system including subscribers telephone lines, link circuits for interconnecting SilldlQlEPllOlle lines in conversational circuit, auton'iatic means operable to control contacts to complete a connection and for maintaining the same during conversation, said means also operable to disassocinte a connected link circuit and a calling and called subscribers line when said subscribers are on different lines but inoperable if said subscribers are on the same line.

12. In a telephone system including subscribei-s telephone lines, link circuits for interconnecting thesamc, automatic ringing means for signaling a called subscriber on a line other than that of the calling subscriber or for ringing a subscriber on the same line with the calling subscriber, link disconnect means indvidual to said link circuits andoperable to control contacts to complete a connection and to maintain the same during conversation and also operable to disassociate a connected link circuit from callinn and called subscribefis lines when said subscribers are on different lines but inoperable if the subscribcns are on the same line.

Signed by me at Chicano, in the county of Cook and State of Illinois, this 14th day of September, 1922.

ELMER W. LINCOLN. 

